How do I use extern functions in a DLL?
printf is an excellent example.

I'm able to build a dll and create an export library for it.
I'm also able to link my test program against it and even
call the functions in the dll as long is it don't use any
external functions. calling printf or any other external
function from my dll leads to
Error: Access violation

What did I miss?

Lars Ivar Igesund

Lars Ivar Igesund wrote:

> How do I use extern functions in a DLL?
> printf is an excellent example.
> 
> I'm able to build a dll and create an export library for it.
> I'm also able to link my test program against it and even
> call the functions in the dll as long is it don't use any
> external functions. calling printf or any other external
> function from my dll leads to
> Error: Access violation
> 
> What did I miss?
> 
> Lars Ivar Igesund

Here's an example that works for me (as far as I can tell):
http://www.digitalmars.com/drn-bin/wwwnews?D/11884

Change:	import windows;
to:	import std.c.windows.windows;


If this doesn't help, we might be able to help better if you post some code.

-- 
Justin
http://jcc_7.tripod.com/d/

J C Calvarese wrote:

> Lars Ivar Igesund wrote:
> 
>> How do I use extern functions in a DLL?
>> printf is an excellent example.
>>
>> I'm able to build a dll and create an export library for it.
>> I'm also able to link my test program against it and even
>> call the functions in the dll as long is it don't use any
>> external functions. calling printf or any other external
>> function from my dll leads to
>> Error: Access violation
>>
>> What did I miss?
>>
>> Lars Ivar Igesund
> 
> 
> Here's an example that works for me (as far as I can tell):
> http://www.digitalmars.com/drn-bin/wwwnews?D/11884
> 
> Change:    import windows;
> to:    import std.c.windows.windows;

Burtons example won't link if I try to use printf. If I don't,
it links but says that there is no start address. (I use export
instead of a .def file.)

What DOES link, is this:

bar.d
----------------
import std.c.stdio;

export void p()
{
  printf("print something\n");
}
----------------
dll.d
----------------
import std.c.windows.windows;

HINSTANCE g_hInst;

extern (C)
{
  void gc_init();
  void gc_term();
  void _minit();
  void _moduleCtor();
}

export:
extern (Windows)
BOOL DllMain(HINSTANCE hInstance,
             ULONG ulReason,
             LPVOID pvReserved)
{
  switch (ulReason)
  {
    case DLL_PROCESS_ATTACH:
    gc_init();
    _minit();
    _moduleCtor();
    break;

    case DLL_PROCESS_DETACH:
    gc_term();
    break;

    case DLL_THREAD_ATTACH:
    case DLL_THREAD_DETACH:
    return false;
  }
  g_hInst = hInstance;
  return true;
}
-------------------

Then I do this:

dmd -L/implib -ofbar.dll bar.d dll.d

To test, I do this:

ptest.d
-------------------
import bar;

int main() {

  p();

  return 0;
}
-------------------

and do this:
dmd -L+bar -ofptest.exe ptest.d

Executing ptest.exe results in
Error: Access Violation

Lars Ivar Igesund

Lars Ivar Igesund wrote:
> J C Calvarese wrote:
> 
>> Lars Ivar Igesund wrote:
>>
>>> How do I use extern functions in a DLL?
>>> printf is an excellent example.
>>>
[...]
> 
> and do this:
> dmd -L+bar -ofptest.exe ptest.d
Try:
dmd -L+bar -ofptest.exe ptest.d bar.d

I can't explain WHY adding bar.d to the command line makes it work, but apparently it does. This seems like either a compiler bug or a linker bug that doesn't show up until runtime.

Output:
F:\pgm\d\testing\newsgroup\dll_printf>dmd -L/implib -ofbar.dll bar.d dll.d
d:\dmd\bin\..\..\dm\bin\link.exe bar+dll,bar.dll,,user32+kernel32/noi/implib;

F:\pgm\d\testing\newsgroup\dll_printf>dmd -L+bar -ofptest.exe ptest.d bar.d
d:\dmd\bin\..\..\dm\bin\link.exe ptest+bar,ptest.exe,,user32+kernel32/noi+bar;

F:\pgm\d\testing\newsgroup\dll_printf>ptest.exe
print something

> Lars Ivar Igesund

-- 
Justin
http://jcc_7.tripod.com/d/

J C Calvarese wrote:
> Lars Ivar Igesund wrote:
> 
>> J C Calvarese wrote:
>>
>>> Lars Ivar Igesund wrote:
>>>
>>>> How do I use extern functions in a DLL?
>>>> printf is an excellent example.
>>>>
> [...]
> 
>>
>> and do this:
>> dmd -L+bar -ofptest.exe ptest.d
> 
> Try:
> dmd -L+bar -ofptest.exe ptest.d bar.d
> 
> I can't explain WHY adding bar.d to the command line makes it work, but apparently it does. This seems like either a compiler bug or a linker bug that doesn't show up until runtime.

Yes, I know that this works. But I suppose that that is because bar.d
is compiled into the executable. In this case ptest.exe works without
bar.dll/lib too, so I suppose the dll isn't used at all.

Interestingly enough, embracing the printf in a try/catch block,
makes ptest execute without output or errors. I guess this suggest
some runtime exception/error of some sort, but the provided info
isn't really enough to think anything.

Lars Ivar Igesund

Lars Ivar Igesund wrote:
> J C Calvarese wrote:
[...]
>>> dmd -L+bar -ofptest.exe ptest.d
>>
>>
>> Try:
>> dmd -L+bar -ofptest.exe ptest.d bar.d
>>
>> I can't explain WHY adding bar.d to the command line makes it work, but apparently it does. This seems like either a compiler bug or a linker bug that doesn't show up until runtime.
> 
> 
> Yes, I know that this works. But I suppose that that is because bar.d
> is compiled into the executable. In this case ptest.exe works without
> bar.dll/lib too, so I suppose the dll isn't used at all.

Sorry, I didn't realize that my fix wasn't a fix at all. It sounds like a bug to me. You might try reposting your example with a "[bug] creating a dll in d" topic to have a better chance of getting Walter's attention.

I don't think many people have been using D to create .dll's to use in D. I've created a .dll in C to use D. That worked. I've used existing .dll's (compiled in C) in D. I know others have done the same. Delphi .dll's can be used in D.

D .dll's should be usable in D, but there might be a bug preventing this.

> 
> Interestingly enough, embracing the printf in a try/catch block,
> makes ptest execute without output or errors. I guess this suggest
> some runtime exception/error of some sort, but the provided info
> isn't really enough to think anything.
> 
> Lars Ivar Igesund

-- 
Justin
http://jcc_7.tripod.com/d/

In article <c1pi9b$2808$1@digitaldaemon.com>, Lars Ivar Igesund says...
>
>J C Calvarese wrote:
>> Lars Ivar Igesund wrote:
>Yes, I know that this works. But I suppose that that is because bar.d is compiled into the executable. In this case ptest.exe works without bar.dll/lib too, so I suppose the dll isn't used at all.

Hi!

I have the same problem with exported classes in a library (dll). I have no plan
for a solution. :-( Sorry.

Uwe